Diabetes Inspidus is a disease associated with excessive urination due to the in
ID: 147481 • Letter: D
Question
Diabetes Inspidus is a disease associated with excessive urination due to the inability of the body to properly reabsorb water in the kidneys. In normal individuals, in response to dehydration, the small protein vasopressin is secreted into the blood stream by cells of the hypothalamus. Once in the blood stream vasopressin travels to the kidney and signals water re-absorption. Imagine you are a doctor of a diabetes insipidus patient. You take a hypothalamus cells from a normal patient and your diabetes insipidus patient and induced dehydration. You then perform immunofluorescence using a fluorescently labeled antibody that binds to the vasopressin protein. Immunofluorescence is performed ~40 minutes following the induction of dehydration.
What is wrong with your patient's hypothalamus cells that cause them to have diabetes insipidus? If you were the doctor of the diabetes insipidus patient, how might you treat her to prevent excessive urination?
Explanation / Answer
There are two cases for diabetes insipidus. One is nephrogenic diabetes insipidus and second is central or neurogenic diabetes insipidus. Since the problem does not state which case of diabetes insipidus the patient has, we'll describe both.
1)Nephrogenic : As mentioned in the question, due to dehydration, the vasopressin hormone gets released from the hypothalamus and goes to the kidneys through the blood stream. But in this condition, the sensors for this hormone in the kidneys don't work and hence it is as same as vasopressin not released. Hence water is not reabsorbed and there is excessive dehydration.
Hence, if this is the case, the hypothalamus cells of the patient will be as good as normal with proper release of vasopressin due to dehydration. The treatment options for this are limited since giving more vasopressin doesn't help as kidneys don't respond to it. But non steroidal anti inflammatory drugs can be given sometimes to reduce excessive urination.
2) Neurogenic(central): In this case, the hypothalamus cells are defective and do not release vasopressin. In this case also kidneys dont re-absorb water and leads to dehydration and diabetes insipidus. The cause for this could be an injury in the hypothalamus cells due to surgery, tumor, inflammation or head trauma. Hence in this case, there won't be any fluorescence observed following the induction of dehydration as no vasopressin is released.
In this case, desmopressin is prescribed, which is a type of vasopressin. It acts as a substitute to vasopressin hormone and helps in proper re-absorption of water. And frequent intake of water is also advised.